Chromatic dispersion compensating and chromatic dispersion slope compensating fiber

Abstract

A chromatic dispersion compensating and dispersion slope compensating optical fiber comprises a central core having an index difference Δn 1 with an outer optical cladding, a first buried inner cladding having an index difference Δn 2 with the outer cladding, a ring having an index difference Δn 3 with the outer cladding and a second buried inner cladding having an index difference Δn 4 with the outer cladding. The index difference between the first buried inner cladding and the outer cladding Δn 2 is less than or equal to −13.5.10 −3 and the index difference between the second buried inner cladding and the outer cladding Δn 4 is less than or equal to −3.10 −3 . The fiber has, for a wavelength of 1550 nm, a chromatic dispersion less than or equal to −50 ps/nm/km and a ratio of the chromatic dispersion over the chromatic dispersion slope DOS less than or equal to 70 nm. The second deeply buried inner cladding allows obtaining a low DOS value whilst maintaining acceptable optical characteristics.

1. A dispersion compensating optical fiber comprising:
 a central core having an index difference Δn 1  with an outer optical cladding; 
 a first buried inner cladding having an index difference Δn 2  with the outer cladding; 
 a ring having an index difference Δn 3  with the outer cladding 
 a second buried inner cladding having an index difference Δn 4  with the outer cladding; 
 wherein the index difference between the first buried inner cladding and the outer cladding Δn 2  is less than or equal to −13.5×10 −3  and the index difference between the second buried inner cladding and the outer cladding Δn 4  is less than or equal to −3×10 −3 ; 
 the fiber having, at a wavelength of 1550 nm: 
 a negative chromatic dispersion being less than or equal to −50 ps/nm/km; and 
 a ratio of chromatic dispersion over the slope of the chromatic dispersion (DOS) being less than or equal to 70 mm. 
 
   
   
     2. The fiber of  claim 1 , having at a wavelength of 1550 nm a chromatic dispersion being less than or equal to −100 ps/nm/km. 
   
   
     3. The fiber of  claim 1 , having at a wavelength of 1550 nm a ratio of chromatic dispersion over the slope of the chromatic dispersion (DOS) being less than or equal to 55 nm. 
   
   
     4. The fiber of  claim 1 , wherein the index difference between the central core and the first buried inner cladding Δn eq =Δn 1 −Δn 2  is in a range from 35.10×10 −3  to 51×10 −3 . 
   
   
     5. The fiber of  claim 1 , wherein the effective surface for the fundamental of propagation is more than or equal to 12 μm 2 . 
   
   
     6. The fiber of  claim 5 , wherein the effective surface for the fundamental of propagation is more than or equal to 14 μm 2 . 
   
   
     7. The fiber of  claim 1 , wherein the effective cut-off wavelength is less than or equal to 1650 nm. 
   
   
     8. The fiber of  claim 1 , wherein the bending losses at a wavelength of 1625 nm for a curvature radius of 10 mm are less than or equal to 500 dB/m. 
   
   
     9. The fiber of  claim 8 , wherein the bending losses at a wavelength of 1625 nm for a curvature radius of 10 mm are less than or equal to 200 dB/m. 
   
   
     10. The fiber of  claim 1 , wherein the figure of merit at a wavelength of 1550 nm is more than or equal to 100 ps/rn/dB. 
   
   
     11. The fiber of  claim 10 , wherein the figure of merit at a wavelength of 1550 nm is more than or equal to 150 ps/nm/dB. 
   
   
     12. The fiber of  claim 1 , wherein the central core has a trapezoid shape. 
   
   
     13. The fiber of  claim 1 , wherein the central core has a step shape. 
   
   
     14. The fiber of  claim 1 , wherein the central core has an alpha shape. 
   
   
     15. A transmission system comprising:
 an optical transmitter emitting optical signals in a predetermined range of wavelength; 
 a transmission optical fiber having for said predetermined range of wavelength a positive chromatic dispersion and a positive dispersion slope with a ratio of chromatic dispersion over the slope of the chromatic dispersion (DOS) being less than or equal to 70 nm; 
 the dispersion compensating fiber of  claim 1 . 
 
   
   
     16. The system of  claim 15 , wherein the transmission optical fiber is a NZDSF+. 
   
   
     17. A chromatic dispersion compensating module for transmission optical fiber having in a predetermined range of wavelengths a positive chromatic dispersion and a positive chromatic dispersion slope with a ratio of chromatic dispersion over the chromatic dispersion slope (DOS) of less than or equal to 70 nm, the module containing a single fiber consisting in a portion of the fiber of  claim 1 .